The US Supreme Court refused to hear an appeal that sought to keep 50 of Arthur Conan Doyle’s Sherlock Holmes stories under copyright. So the stories, all published before 1923, are no longer protected by copyright. The suit was filed by the Arthur Conan Doyle Estate, which objected to a book scheduled for last year that had contemporary writers taking on the Holmes tales.
In the Company of Sherlock Holmes was to be published by Pegasus Books, but was delayed while the suit played out. Nothing is stopping it now, plus it has a little extra publicity. The Conan Doyle Estate still holds the copyright for the Sherlock Holmes stories published from 1923 to 1927–the final Holmes tales. The other stories are now in the public domain.